Key takeaways
- Ties: Two or four fabric ties wrap around back posts or slats. Check tie spacing against your bench posts.
- Non-slip backing: A rubberized bottom helps on smooth metal or plastic benches.
- Hook-and-loop straps: Easier to remove quickly before storms.
- Gussets vs knife edge: Boxed (gusseted) cushions sit flat and look tailored; knife-edge cushions taper at the edges and suit thinner, casual benches.
A 48 x 18 outdoor bench cushion fits most 4-foot, two-seat garden benches and porch benches whose seat measures about 47–50 inches long and 17–20 inches deep; if your seat is deeper than about 21 inches, a 48 x 24 cushion is the better match, and if it is closer to 40 inches long, choose 40 x 18. The quick way to decide is to measure the seat itself, not the bench, and compare it with the size table below.
How to Measure Your Bench Seat
- Length: Measure the flat seating surface from inside of one arm to inside of the other. On armless benches, measure the full seat slats.
- Depth: Measure from the front edge of the seat to where the back meets the seat. If the back slopes, measure at seat level.
- Back posts and supports: Note any posts that rise from the seat, which need cut-outs or ties.
- Height under the table or overhang: On dining benches and window seats, measure the space between the seat and anything above it so a thicker cushion still fits.
Cushions are usually sold by nominal size, so a “48 x 18” cushion may be 47–48 inches by 17.5–18 inches once sewn. Aim for a cushion that is equal to or up to about 1 inch smaller than the seat in each direction. Oversized cushions bunch against the arms and back; undersized cushions slide.
Which Size Fits Which Bench
| Cushion size | Fits seats measuring about | Common benches | Seats |
|---|---|---|---|
| 40 x 18 in | 39–42 x 17–19 in | Compact garden benches, bistro benches, entry benches | 2 snug adults or 1 adult + child |
| 44 x 18 or 19 in | 43–46 x 18–20 in | 4 ft benches with thick arms, porch swings | 2 adults |
| 48 x 18 in | 47–50 x 17–20 in | Standard 4 ft garden and porch benches, picnic benches | 2 adults |
| 48 x 24 in | 47–50 x 22–25 in | Deep porch benches, window seats, daybed-style benches | 2 adults, room to lounge |
| 51–60 x 18 in | 50–60 x 17–20 in | 5 ft benches and 3-seat porch swings | 3 adults |
48 x 18 vs 48 x 24: The Depth Question
Most outdoor benches built for upright sitting have seats 17–20 inches deep, matching dining chairs. The 48 x 18 size suits these. A 24-inch-deep cushion is meant for deeper seats: a porch bench with a laid-back design, a built-in window seat or a storage bench with a deep lid. Putting a 24-inch cushion on an 18-inch seat leaves 6 inches overhanging the front edge, which folds down and wears quickly.
If your bench seat measures around 20–21 inches deep, a 48 x 20 or 48 x 21 cushion, sold by several cushion makers, gives the cleanest fit; otherwise choose the 18-inch depth and accept a small reveal at the back.
Thickness and Seat Height
Thickness changes comfort and seat height. Comfortable outdoor seat height is usually 17–19 inches from the ground to the top of the compressed cushion.
| Thickness | Feel | Adds to seat height (compressed) | Best for |
|---|---|---|---|
| 2 in | Firm, minimal | About 1–1.5 in | Dining benches, benches with low backs |
| 3 in | Balanced | About 2–2.5 in | Most garden and porch benches |
| 4 in | Plush | About 3 in | Low benches (seat under 15 in), lounging |
| 5 in or more | Very soft | About 4 in | Deep window seats; may push you forward on upright benches |
On a bench with a fixed back, a thick cushion moves you forward and up, which can leave the backrest too low. If your bench back is low or upright, stay with 2–3 inches.
Fill and Fabric for Outdoor Use
| Fill type | Drying speed | Holds shape | Typical price, 48 x 18 |
|---|---|---|---|
| Polyester fiberfill (tufted) | Moderate | Flattens in 1–2 seasons | $25–$50 |
| Polyurethane foam, wrapped | Slow unless covered by a liner | Good | $40–$90 |
| Reticulated (open-cell, quick-dry) foam | Fast; water drains through | Very good | $80–$180 |
For fabrics, solution-dyed acrylic such as Sunbrella resists fading longest in full sun. Spun polyester costs less and looks good for a few seasons but fades faster. Olefin sits between the two. For a covered porch, polyester fiberfill cushions are fine; for an open garden bench that gets rained on, quick-dry foam with a solution-dyed fabric lasts much longer.
Keeping the Cushion in Place
- Ties: Two or four fabric ties wrap around back posts or slats. Check tie spacing against your bench posts.
- Non-slip backing: A rubberized bottom helps on smooth metal or plastic benches.
- Hook-and-loop straps: Easier to remove quickly before storms.
- Gussets vs knife edge: Boxed (gusseted) cushions sit flat and look tailored; knife-edge cushions taper at the edges and suit thinner, casual benches.
Quick Size Decision
| Your measurement | Buy |
|---|---|
| Seat 39–42 in long, about 18 in deep | 40 x 18 |
| Seat 47–50 in long, 17–20 in deep | 48 x 18 |
| Seat 47–50 in long, 22–25 in deep | 48 x 24 |
| Seat 43–46 in long | 44 x 18 or 19, or a custom size |
| Seat over 50 in long | 51–60 in cushion or two smaller cushions |
Care and Storage
Stand cushions on edge after rain so water drains, and bring them in or store them in a deck box during long wet spells and winter. Brush off pollen and debris regularly, and wash removable covers on a gentle cycle, air-drying them to avoid shrinkage. A cushion stored dry between uses keeps its color and loft for several more seasons than one left out year-round.
